daganasrm2009abstracto268 12564089438001-phpapp02
TRANSCRIPT
Comprehensive chromosomal screening at the blastocyst stage
Dagan Wells, PhD, FRCPath
Less than half the chromosomes tested
Spreading requires skill and can be inconsistent
Limitations of conventional embryo screening techniques
Cells are in interphase
Mosaicism
Limited range of fluorochromes
Poses a significant problem for diagnosis. However, most mosaic cleavage stage embryos are aneuploid in every cell.
- use FISH
Cleavage stage biopsy may represent a cost to the embryo
Kallioniemi et al 1992; Wells et al 1999, 2002; Voullaire et al 1999; Wilton et al 2001; Gutierrez et al 2004, 2005; Fragouli et al 2006, 2007
• Technique related to FISH
• Allows the copy number of every chromosome to be determined
Normal Trisomy Monosomy
Normal DNATest DNA
Comparative genomic hybridization- CGH
Gai
n
Los
sN
orm
al
Chromosome 15
Embryo screening using CGH
• All chromosomes tested
Benefits
• DNA-based
• No spreading of cells on slides
But what about mosaicism and the impact of biopsy?
Comprehensive chromosome screening of blastocysts
Trophectoderm biopsy-
3-10 cells (mean 5) biopsied and tested
Courtesy of M. Katz-Jaffe and J. Stevens, CCRM
Diagnosis more robust and accurate
• Biopsy of several cells is possible
Less risk of misdiagnosis due to mosaicism
Analysis of blastocyst stage
• Can overcoming the principal challenges to accurate screening allow PGS to fulfill the potential predicted by theory?
Reduced impact of embryo biopsy
• Blastocyst cryopreservation (vitrification) necessary
Comprehensive chromosome screening of blastocysts
•Near 100% survival after biopsy, freeze and thaw
• 170 patients, mean age 38 years, 1-6 previous failed IVF cycles (mean 2)
• Pregnancy rate per cycle with transfer 87%
• Birth rate per cycle with transfer 79%
• Implantation rate per embryo 67%
Blastocyst CGH- clinical results
72%
60%
28% *
Control group matched for: maternal age, day-3 FSH, day of transfer, # oocytes retrieved, # of failed cycles
*p<0.0003 - Extremely promising for single embryo transfer
• Embryo loss rates are low
• 91% of embryos that produced a fetal sac resulted in an ongoing third trimester pregnancy or live birth
• 97% of embryos that produced a fetal heart beat resulted in an ongoing third trimester pregnancy or live birth
• Expected pregnancy loss rate for IVF patients in this age range is ~25%
Blastocyst CGH- rates of pregnancy loss
Blastocyst CGH- Pregnancy rates
0
2
4
6
8
10
12
30-34 35-38 39-42 43-500
10
20
30
40
50
60
70
80
90
100
Positive pregnancy per transfer
Positive pregnancy per cycle with biopsy
Pregnancy rate per transfer shows only a small decline with advancing age
Pregnancy rate per cycle shows a significant decline
Blastocyst CGH- aneuploidy and implantation rates
0
2
4
6
8
10
12
30-34 35-38 39-42 43-500
10
20
30
40
50
60
70
80
90
100
Implantation rate
Aneuploidy rate
Cycles with all embryos aneuploid
Why does age still lead to reduced pregnancy rates despite aneuploidy screening?
• Pregnancy rates were above those typically achieved for all age groups.
• However, pregnancy rates were lower for older patients due to the increased frequency of cycles with no euploid embryos.
• Spontaneous abortion rates were reduced for all patients, including those with a history of multiple miscarriage
• Chromosomally normal embryos from older patients have a similar chance of producing a child as those derived from young patients.
• Aneuploidy is likely to be the principal factor causing reduced IVF success with advancing maternal age
Conclusions
• Can the results obtained in the current study be replicated in a randomized controlled trial?
• An RCT is currently underway
• What patient groups will benefit the most from this type of screening?
• Young patients may benefit, particularly in countries where single embryo transfer is mandatory
Questions
United Kingdom (Oxford)Elpida Fragouli
Samer Alfarawati
United States (Livingston, NJ)Pere Colls
Tomas EscuderoN-neka Esprit-Ngachou
Jill FischerCristina Gutierrez-Mateo
Santiago MunneRenata PratesJorge Sanchez
Sophia TormasiJohn Zheng
Colorado Center for Reproductive Medicine
Mandy Katz-JaffeJohn Stevens
Bill Schoolcraft